378 



Col. Sir D. Bruce and others. 



[Apr. 18, 



Remarks. — Sixty laboratory-bred flies were fed daily for five days on an infected 

 monkey. They became infective on the 29th day. On the 34th day one fly which had 

 died was found to be infected with flagellates, but on injection into a monkey it failed to 

 give rise to Sleeping Sickness. No infected flies were found among the 28 remaining 

 alive on the 38th day, when they were dissected. 



Experiment 1761. 



Date. 



Day 

 of experi- 

 ment. 



Procedure. 



Result. 



Remarks. 



Positive. 



Negative. 



1909. 

 Oct. 1—5 



„ 6-7 

 8— 

 Nov. 8 

 Nov. 9—10 



1—4 



5—6 

 7—38 



39—40 



Flies fed on infected 



monkey 

 Flies starved. 

 Flies fed on healthy 



monkey, 1761 

 Flies starved. 



-1- 





50 flies used. 



Nov. 11, 31 remaining 

 flies killed and dis- 

 sected ; all negative. 



Remarks. — Fifty laboratory-bred flies were -fed daily for five days on an infected 

 monkey. They became infective on the 38th day. No infected flies were found among 

 the 31 remaining alive on the 41st day, when they were dissected. 



Table IV. — Number of Flies found Infected with Trypanosoma gambiense in 

 the Experiments with Laboratory-Bred Flies. 



Experiment. 



No. of 

 flies used. 



Experiment, 



positive 

 or negative. 



No. of 

 infected flies 

 found. 



Result 

 of injection of 

 infected flies. 



Remarks. 



975 



16 



-1- 



0 





12 remaining flies 













pooled. 



1269 



22 





2 



Negative. 





14,52 



90 





1 



it 





] 549 



50 



+ 



4 



Positive. 





1 5(i(i 



35 



+ 



9 



Negative 



1 fly injected. 



am 



50 



-t- 



6 



Positive. 





imi 



60 



+ 



4 





Flies not injected. 



1672 



28 





2 



Negative. 



] (i80 



45 





1 







] (i93 



50 





2 







J 706 



60 





4 







1712 



50 



+ 



1 



ti 





1 760 



60 



+ 



1 







1769 



60 





2 



Positive. 





1801 



70 





1 





Fly not injected. 



There are some curious results to 1«! noted liere. In Experiment 975 the 

 twelve I'ciniu'iiiiiir iUvH were dissected and cxiuninod. None was found 



